Question

我有一个表Inputs和一个派生表参数

CREATE TABLE Configurables
(
  id SERIAL PRIMARY KEY
);

CREATE TABLE Inputs
(
  configurable integer REFERENCES Configurables( id ),
  name text,
  time timestamp,
  PRIMARY KEY( configurable, name, time )
);

CREATE TABLE Parameters
(
  configurable integer,
  name text,
  time timestamp,
  value text,
  FOREIGN KEY( configurable, name, time ) REFERENCES Inputs( configurable, name, time )
);

以下查询检查参数是否已更改或尚未存在，并使用新值插入参数。

QString PostgreSQLQueryEngine::saveParameter( int configurable, const QString& name, const QString& value )
{
  return QString( "\
    INSERT INTO Inputs( configurable, name, time ) \
      WITH MyParameter AS \
      ( \
        SELECT configurable, name, time, value \
        FROM \
        ( \
          SELECT configurable, name, time, value \
          FROM Parameters \
          WHERE (configurable = %1) AND (name = '%2') AND time =  \
          ( \
            SELECT max( time ) \
            FROM Parameters \
            WHERE (configurable = %1) AND (name = '%2') \
          ) \
          UNION \
          SELECT %1 AS configurable, '%2' AS name, '-infinity' AS time, NULL AS value \
        )AS foo \
      ) \
      SELECT %1 AS configurable, '%2' AS name, 'now' AS time FROM MyParameter \
      WHERE time = (SELECT max(time) FROM MyParameter) AND (value <> '%3' OR value IS NULL); \
      \
    INSERT INTO Parameters( configurable, name, time, value ) \
      WITH MyParameter AS \
      ( \
        SELECT configurable, name, time, value \
        FROM \
        ( \
          SELECT configurable, name, time, value \
          FROM Parameters \
          WHERE (configurable = %1) AND (name = '%2') AND time =  \
          ( \
            SELECT max( time ) \
            FROM Parameters \
            WHERE (configurable = %1) AND (name = '%2') \
          ) \
          UNION \
          SELECT %1 AS configurable, '%2' AS name, '-infinity' AS time, NULL AS value \
        )AS foo \
      ) \
      SELECT %1 AS configurable, '%2' AS name, 'now' AS time, '%3' AS value  FROM MyParameter \
      WHERE time = (SELECT max(time) FROM MyParameter) AND (value <> '%3' OR value IS NULL); \
    " ).arg( configurable ).arg( name ).arg( value );
}

我应该如何最好地解决MyParameter子查询的重复问题？

有关清理此类查询的其他任何提示

Answer 1

您应该避免使用非规范化表格。您应该使用视图来轻松查看参数表。这会更容易。

如果您的视图速度不够快，您应该只使用反规范化的摘要表。但是，任何非规范化的表都应该使用触发器来维护，否则你会冒这个表不同步的风险。

为此，您可以在Parameters上创建一个触发器，该触发器会在插入时upsert进入Inputs。如果您在Parameters上删除或更新此列，则维护Inputs会很复杂。如果Parameters中没有相应的行，则必须删除行 - 您需要在Inputs中维护计数，以了解Parameters中何时没有相应的行。并发插入/更新/删除性能会很糟糕，因为Parameters中的任何更改都必须阻止Inputs中的行。这一切都是丑陋和糟糕的 - 视图是更好的解决方案。

如何解决以下PostgreSQL查询中的代码重复问题？

1 个答案: